The present invention is related to systems and methods for determining the validity of a signal, and more particularly to systems and methods for determining an out of band condition of an input signal.
Currently, various systems utilize serial links that define out of band signaling. For example, a serial ATA link is a high speed link that may be used in relation to various storage devices such as hard disk drives. Out of band signals are incorporated within the signaling scheme and are used to complete initialization and to negotiate link speed. In a typical system, the out of band signals are data bursts unrelated to the data being transferred (hence the name out of band) that are interspersed with idles exhibiting a voltage below a particular known level. The time durations of the out of band bursts are typically fixed, but the duration of the intervening idles may vary. To use the out of band signaling, it is necessary to detect peak thresholds of a received data signal. Thus, systems relying on out of band signaling generally incorporate a circuit including an amplifier and a peak detector capable of identifying out of band signals. In a typical implementation, an input signal includes a burst of out of band information with a frequency of 1.5 Gbps. Existing circuits designed to detect the aforementioned information include an amplifier and a peak detector. An amplifier operating at 1.5 Gbps consumes considerable power. Further, such an amplifier often requires customization when it is used in different designs. Yet further, a peak detector capable of operating at 1.5 Gbps is not easily implemented.
Turning to FIG. 1, a prior art out of band detection circuit 100 is depicted. Out of band detection circuit 100 includes a capacitor 110 that AC couples an input signal 105 to a summing node 115. Detection/Hysteresis 120 is subtracted from input signal 105 at summing node 115. The difference between input signal 105 and Detection/Hysteresis 120 is amplified by an amplifier 125. In typical implementations, amplifier 125 is a multi-stage amplifier. The output of amplifier 125 drives a peak detector circuit 130 that is operable to identify a peak value of the amplified sum of input signal 105 and Detection/Hysteresis 120. The detected peak value is provided to a comparator 135 where it is compared against a reference signal 140. Reference signal 140 may be developed by replicating circuitry in peak detector 130 that allows it to track operation over a wide variety of temperature and process. Where the output of peak detector 130 exceeds that of reference signal 140, an out of band signal 145 is asserted.
Hence, for at least the aforementioned reasons, there exists a need in the art for advanced systems and methods for determining an out of band signal.